Please add a "none" pseudo tag

Having a “none” or similar name pseudo tag would be of great help for filtering.

Right now, there is no way to create a filter to select articles that have no tags.

That is a limitation and make it more difficult to create collections and routes.
If you have two collections based on col1 and col2 tags, the only way to create a filter that selects articles with no tag is:
filter: tag:-col2+tag:-col2

And that is not exactly selection of articles that have no tag assigned, as there may be other tags assigned.

In the admin interface there is no way to filter the posts to see the ones that have no tag.

There is a “all posts” pesudo tag, but not a “none” one.

It would be great to have it in the admin interface, and in filters too to be able to do something like:

filter: tag:none

Or may be

filter: tag:

or something like that.

Thank you